Prior art of possible relevance includes the following U.S. Pat. Nos. 3,007,065 issued Oct. 31, 1961 to Rigney; 3,043,968 issued July 10, 1962 to Ward; 3,261,295 issued July 19, 1966 to White; 3,588,290 issued June 28, 1971 to Kreutzkampf; 3,629,628 issued Dec. 21, 1971 to Rank; 3,648,085 issued Mar. 26, 1970 to Fuji; 4,139,789 issued Feb. 13, 1979 to Hunt; and 4,394,593 issued July 19, 1983 to Gocho.
The cooling of various parts of dynamoelectric machines has long been recognized as being advantageous. By cooling various components, the capacity of a given machine is increased because the heat generated during operation which might otherwise destroy or damage the machine at a given capacity level is carried away by the coolant.
This increase in capacity is particularly advantageous in aircraft generators. In such a use, the weight of the generator is a substantial concern. Thus, for a desired capacity necessary to meet electrical consumption requirements on an aircraft, the weight of the generator may be minimized by increasing the effectiveness of its cooling system.
Typical generators employed in aircraft are so-called "brushless" generators. They frequently include a stator which inclues a main armature, an exciter field, and a permanent magnet generator armature. The rotor includes a permanent magnet field, an exciter armature and a main field winding. In addition, the rotor will include a full or a half wave rectifier, usually a full wave rectifier, which interconnects the exciter armature and the main field winding to allow the former to energize the latter while at the same time rectifying the alternating current generated in the exciter armature to direct current before it is applied to the main field winding.
To adequately cool the rotor, it is necessary that both the exciter armature and the main field winding be cooled. It is also necesary to cool the rectifier.
While the rectifier is always electrically interposed between the exciter armature and the main field winding, it frequently will be physically interposed as well. Physical interposition of the rectifier frequently poses difficulty in providing for the flow of a coolant along the full length of the rotor shaft carrying the exciter armature and the main field winding while achieving a minimal pressure drop in the rotor coolant flow path from the inlet to the outlet, which minimal pressure drop maximizes machine efficiency.
The present invention is directed to overcoming one or more of the above problems.